Design methodology for reinforced railway tracks based on threshold stress approach

The success of a design methodology for railway track depends on its ability to keep the maximum deviator stress induced on the subgrade due to rail traffic below the threshold stress of the subgrade soil. Considering this, the present study proposes a new design methodology using geosynthetic reinforcement in the track layers to adopt a suitable formation thickness. Geosynthetic reinforcement in one or two layers at suitable interfaces in the track section has been used to reduce the induced deviator stress to acceptable limits. The new method is advantageous in reducing the requirement for formation layer thickness by incorporating geosynthetics. This method also proposes two methods of track design: direct and indirect. The direct method of design uses design charts developed on the basis of numerical and experimental results, whereas the indirect method makes use of empirical equations developed by a computational intelligence technique, Genetic Programming (GP). The accuracy of the indirect method is tested by comparing it with the results of the direct method and verifying by statistical criteria. The indirect method can be very fast to implement for the given set of conditions.